Angel di Maria failed to blossom during his first season at Manchester United but played a crucial role in Argentina's semi-final win(AFP)

Manchester United duo Marcos Rojo and Angel di Maria were both on the score sheet as a Lionel Messi-inspired Argentina thrashed Paraguay to reach the final of the 2015 Copa America.

Former Sporting Lisbon defender Rojo got the rout started after just 15 minutes when he fired past Justo Villar following a Messi free kick, while Di Maria helped himself to an early second half brace with Gerardo Martino's side leading 2-1 following goals from Javier Pastore and Lucas Barrios.

A stunned Paraguay, penalty shootout victors over a virus-plagued Brazil at the weekend, lost both experienced captain Roque Santa Cruz and quarter-final hero Derlis Gonzalez to injury early on and did not recover, with Sergio Aguero of Manchester City and Napoli's Gonzalo Higuain completing the scoring.

Argentina will now face Chile in the final on 4 July at the Estadio Nacional in Santiago after the hosts beat Peru 2-1, courtesy of two goals from Eduardo Vargas.

Despite such an impressive result however, Martino, who managed Paraguay for five years between 2006-11, still believes his side need to improve if they are to win their first Copa in 22 years.

"Our play was much better than in the match against Colombia," he said after the game as reported by Eurosport.

"But in terms of winning back the ball, anywhere on the pitch, I think we were better in the game against Colombia than in today's game. We didn't press well, either when we were in their half of the pitch or when we were forced backwards.

"I'm happy about the 6-1 scoreline and playing in the final but if there's something that needs correcting I'll correct it, whether we draw 0-0, lose or win."

Paraguay coach Ramon Diaz remained upbeat after the final whistle, insisting that the country should be proud of his team and insisting that they will be fully focused on the third-place play-off against Peru in Concepcion.

"We were always looking for the result, but this is the beginning of a process and there is still work to do," he said according to Goal.

"The team showed great dedication, hard work, so I am proud of this squad. The result may be big, but people in Paraguay have to feel proud of this team. This will help us to grow. We have to analyse the tournament, but we are pleased with the group."

"This Copa America is a wonderful experience for everyone. All the national teams have shown growth and a great World Cup qualification process is coming," he continued. "Today, our opponents showed class and potential, but we are already thinking of Peru – we will do our best to get third place.